Process of preparing storage battery cases and the like



' Patented-Feb. 16, 1943 as PATENT orr cs PROCESS OF PREPARING STORAGE BAT-I TERIOASESANDTHELIKE r Edward 12.. Dillehay, are; Ellyn, 111., assignor to The Richardson Company, Lockland, Ohio, a

corporation of Ohio No Drawing. Application September 1,1938,

. Serial 1%. 228,012

. 5 Claims.

An object of my invention is the provision of an improved moulding and treatment process for moulded articles of which storage'battery' cases are exemplary. I shall describe my invention in connection with storage battery cases of bituminous type made in accordance with the teachings of the Lukens Patent No. 1,752,917; but itwill be understood that my invention is applicable to storage battery cases otherwise made and to moulded articles generally wherein a quick set is desired.

It is an object of my invention to provide a quick setting treatment which will harden a thermoplastic moulding binder without imposing defleeting strains on the moulded article.

It is an object of my invention to provide a quick setting treatment which is inexpensive and does not add to the cost of manufacture;

It is a further object of my invention to secure improvements in the qualities of moulded articles as will be more fully hereinafter set forth.

It is a further object of my invention to provide a quick setting treatment which will not interfere with nor delay after treatments.

These and other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading this specification, I accomplish by that certain series of process steps of which I shall now describe the aforesaid exemplary embodiment, contrasting it with the usual procedure in the manufacture of electric storage battery cases. j

- Hitherto, in the manufacture of bituminous storage battery cases, after the moulding composition has been prepared, and isat the proper temperature for moulding, suitable mould charges are made from it. These mould charges are moulded in a press, with a dwell,'say of the order of 5 to 6 minutes or more. During this time the mould elements are hsually cooled with cooling water run through perforations or hollows in the elements. This: is necessary to give the box a preliminary set, so that the box will tainer may be provided alongside each press, or i between presses; or if desired the conveyor can be caused to submerge the boxes. An immediate submergence of the boxes is to be preferred; and 3 when this is finished, the boxes should be drained. It is convenient to do this by hand before'the boxes are placed on the-conveyor. A quick dip is all that is required; but the boxes can remain submerged as long as desired.

There are several very important advantages which I secure from this procedure. For one thing, the boxes can be moulded in a much shorter time, and on the average with a press dwell of only threeto four minutes instead of the usual minimum of five to six minutes. This, as will be clear, greatly reduces the investment in moulds and presses.

. A dwell of the order of three to four minutes is sufficient to give the moulding composition sufficient rigidity to maintain its shape; but if the boxes were removed from the mould at this stage and given .no after treatment, the surfaces will creep and roughen, or orange peel". This not only gives an unsightly appearance, but makes for acid absorption. However, in my method the quick cooling sets the surface of the moulded article and prevents creeping and toughening, giving a smoother surface than could be obtained by a longer dwell in the mould. Ihave found that a smoother surface on'a battery box causes the box to resist the storage battery acid better, and gives to the box less tendency to developcraeks or points of seepage. I have observed that when a leaky battery box shows up, an examination of the inside of the box will disclose a porous or rough spot opposite the point of deakage on the outside. The better surface obnot deflect of its own weight upon removal from tained through the use of my method greatly minimizes this difficulty.

Again the quick cooling of the storage battery boxes appears greatly to minimize'the formation a of "hair-line cracks around the tops of the nutsidewalls and partitions. This improvement I believe to be due to the fact that when the boxes are pulled" faster they are more flexible and have not yet begun to form the small cracks in the mould. The quick cooling has no tendency to form cracks because when submerged the boxes are unsupported, i. e., not bound in a. mould, and the various portions are free to expand and contract as required.

The use of my process has greatly cut down the rejections of battery boxes. It not only saves time and money on mould equipment, but producal a better product.

' otherwise with a suitable'coating substance as a finishing operation, and for this purpose the! must be dry.

Because oi the waterproof character 0! the moulding composition, when the boxes are dipped in water and drained. some water clings to them in the term of relatively large drops. These dry reach the inspection point. While artificial-drying is feasible, it requires power and entails a of installation. a

I have been able toovercome this diilicultyby employing in connection with the cooling water a wetting agent. A wetting agent causes the water to spread out in an even film on the surface of the box or other article, and when the box is drained there will be no drops which dry slowly on its surface. By way of example, on an accurate test, a storage battery box dipped in plain water and drained in the usual way required over 90 minutes to dry, whereas when one-twentieth of one per cent of an efllcient wetting agent was added to the water, the same box, dipped and drained in the same way dried thoroughly in three minutes, under the same drying conditions. It will be understood that a drying time or this order is well within the time cycle of the travel of the boxes on the conveyors so that by the time the boxes reach the inspection department they are perfectly dry.

There are many wetting agents which will serve the purpose, and in general I can employ any material .which will reduce the surface tension of the water and which will not leave an objectionable film upon the molded article. Specifically, I have been using a wetting agent sold under the trade name "Aerosol and which is an ester of sulpho-bicarboxylic acid.

Modifications may be made'in my invention without departing from the spirit oi it. I

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A process of preparing hollow moulded articles irom continuously thermoplastic moulding compositions which comprises heating a mould charge of the composition, and moulding it in a cooled mould under pressure to shape it, permitting the article to remain in the mould until it has sufllcient rigidity for removal but is insumciently set to develop ultimate surface charactersuiiicient rigidity for removal but is insumciently set to develop ultimate surface characteristics. removing it, and immediately plunging it into a bath of cold water, removing and draining the slowly, and are frequently not dry when the boxes article, and conveying it to a point of inspection.

3. A process of preparing hollow moulded articles from continuously thermoplastic moulding compositions which comprises heating a mould ing transportation.

4. A process of preparing hollow moulded articles from continuously thermoplastic moulding compositions which comprises heating a mould charge of the composition, and moulding it in a cooled mould under pressure to shape it, permitting the article to remain in the mould until it has suiilcient rigidity for removal but is insuifleiently set to develop ultimate surface characteristics, removing it, and immediately plunllnl it into a bath of cold-water. removing and draining the article, and conveying it to a point of inspection, said water containing, a wetting agent whereby drying of the articles is facilitated during transportation, and coating said articles at said inspection point with a protective substance.

5. A process of preparing storage battery cases from a bituminous storagebattery molding composition comprising a bitumen, acid-resistant mineral matter in finely divided form and crime iiber not exceeding substantially 15% or the mass by weight which process comprises forming a heated mold charge from the composition, molding it under pressure in a cold mold with a dwell of the order of three to four minutes, removing the battery case thus formed from the mold and immediately plunging it into water to which a and draining said case.

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